Direct Preference Optimization (DPO) is a reinforcement learning algorithm that aims to optimize the policy directly based on the preferences among trajectories, rather than relying on the reward function.
For example, in a self-driving car application, DPO could be used to optimize the policy for avoiding accidents. Instead of solely relying on the reward function that assigns a positive reward for avoiding an accident and a negative reward for causing one, DPO would use the preferences among trajectories to directly optimize the policy for safe driving.